Eli5: it’s said that creating larger highways doesn’t increase traffic flow because people who weren’t using it before will start. But isn’t that still a net gain?

Question

If people are being diverted from side streets to the highway because the highway is now wider, then that means side streets are cleared up. Not to mention the people who were taking side streets can now enjoy a quicker commute on the highway

In: Engineering

Answer 1

I think the major thing missing from the argument is population growth. If 10,000 new homes are built in the suburbs that will result in many new trips. If you don’t build more lanes people who weren’t using it before will now be using it. Also for things like commuting to work people will go there even if the roads are congested. One of the main highways near me got widened about 25 years ago from 2 to 4 lanes each way and it is still better even though there have been lots of new homes built at the edges of the suburbs. Ideally there would be other options like mass transit but if there isn’t people will drive if they have to.